Food Science Question -- Homemade Champagne Mustard

My grandmother's recipe for champagne mustard requires the dry mustard powder to be soaked in champagne/vinegar overnight. Is there a reason for this? My only guess is the original recipe used mustard seed, not powdered.

Hmmm....that is an interesting mustard.
I have not seen one made with eggs. I still think she means mustard powder because she doesn't mention grinding or pulverizing the seeds. Be sure to report back. I am intrigued by the recipe. :0)

It's seriously good - and in its natural state, fairly hot. Blended 1/2 and 1/2 with mayo -- lovely on salmon. I set out both versions in separate bowls for the delicious pretzel bites I found on this site (can't remember who posted the recipe, but -- yum!) Great on country ham. The list goes on...